Midterm 1 Flashcards
Potential Energy
Stored energy, object gains/loses ability to store E based on its position
molecular: related to the position of shared e- in covalent bonds (farther from nucleus = more PE)
Higher up/farther away something is the more potential E
Beige Adipose Tissue (BAT)
Burns E to produce heat (thermogenesis)
Made from WAT (in cold temps)
White Adipose Tissue (WAT)
Stores E
In warm temperatures what cells do mammals make? In cold temperatures what cells do mammals make?
Cold temps = make more beige adipose cells (generate heat to combat cold)
Warm temps = make more white adipose cells to store energy
Kinetic Energy
Energy of motion
molecules have it bc constantly in motion
KE of molecular motion = thermal E
Atom
Extremely small particles called e- orbit an atomic nucleus made of larger particles called protons and neutrons in the nucleus.
Atomic nucleus
Made up of protons and neutrons or 1 proton (hydrogen) surrounded by orbiting electrons
e- more dense in center of nucleus & less as it gets further away (more PE)
What e- have the most PE?
e- in outermost/valence shell (furthest from nucleus) = more potential E
takes more E for e- to be in outer shell than inner one (bc nucleus has + protons that e- attracted to ) & able to do more reactivity outside
Chemical bond
Attractions that bind atoms together
Ion
An atom / molecule that has lost/gained e- and thus, carries a full electrical charge
cation = positive
anion = negative
Ionic bond
e- are completely transferred from one atom to another, e- transfer occurs bc it gives resulting atoms a full valence shell, 2 opposite charged ions (cation +, anion -)
Tends to happen when 1/2 valence e-
Molecule
Substances held together by covalent bonds
Covalent bond
Shared e- “glue” atoms together, a strong attraction where 2 atoms share electrons, no full charge
Nonpolar covalent bonds
e- are shared EQUALLY between 2 atoms in bond (NO PARTIAL CHARGES)
Electroneg diff 0.5>
Store the most PE bc negatively-charged e- are equally far from both atoms’ positively charged atomic nuclei
Positive & Negative charges attract each other -> energetically unfavorable state, takes a large amount of PE for the e- to remain in this position
Polar Covalent bonds
UNEQUAL sharing of e- (e- more close to the nucleus of more electronegative atom)
No full charge
Ex: H2O
1 atom attracts more electron (partially negative) & other atom is partially positive.
Stores the least PE
Energetically favorable
Electroneg difference 0.5<
Negatively-charged e- are far from one atom’s atomic nucleus, & are much closer to the other atom’s atomic nucleus. Bc positive and negative charges attract each other -> energetically favorable state
Does not take much PE for e- to remain in this position
Electron Shells
Electrons can move around atomic nuclei in specific regions called orbitals (can hold up to 2 electrons) & these orbitals are grouped into levels (shells)
What does the numbering of electron shells tell you?
Orbitals are numbered 1, 2, 3 etc. to indicate their distance from the nucleus (small - closer)
What type of electrons are located in the “valence shell”? How does this relate to the “valence” of an atom?
valence e- are located in valence shell & determine reactivity
The outermost e- as not full (at least one orbital w/ unpaired valence e-)
Valence
of unpaired e- in outermost shell
e- in valence shell “like” to be paired
# unpaired e- in outermost shell
Atomic Bonding
Atoms connected by bonds
stable & more happy when outermost shell = full
Electronegativity
When atoms of different elements form a bond, they may pull shared e- towards their nuclei with varying strengths
- large #s = stronger pull (oxygen sucks = highest )
If difference = 1 or large = Higher polarity
When would you consider a bond is nonpolar in terms of electronegativity?
If the difference is less than 0.5 -> has a smaller polarity and means that there is Higher PE
Bond Energy
not actually in orbits but clouds of e-
more energetic e- spend more time in outer shells (Higher PE)
How does the type of bond affect the location of the e- and how much E the bonds have
if e- far from all atomic nuclei = nonpolar (most PE)
e- close to 1 nucleus & far from another = polar (less PE)
e- very close to nucleus = ionic (lowest PE)
Explain why the energy differs between the bonds, using appropriate terminology.
Nonpolar bonds store the most potential energy, because the negatively-charged electrons are equally far from both atoms’ positively charged atomic nuclei. Because positive and negative charges attract each other, this is an energetically unfavorable state, meaning that it takes a large amount of potential energy for the electrons to remain in this position.
Polar bonds store the least potential energy, because although the negatively-charged electrons are far from one atom’s atomic nucleus, they are much closer to the other atom’s atomic nucleus. Because positive and negative charges attract each other, this is an energetically favorable state, meaning that it does not take much potential energy for the electrons to remain in this position.
Compare and contrast the three major types of chemical bonds between atoms by filling out the table below:
Ionic, Nonpolar cov, Polar cov
- ionic, full charge, unequal
-polar, partial charge, unequal
-nonpolar, no charge, equal
In your own words, explain why there is a partial negative charge on the oxygen atom in a water molecule (H2O).
-Oxygen has a higher electronegativity & attracts e- from hydrogen & has a partial negative charge
Reactant
Any of the starting materials in a chemical RXN
Product
Any of the final materials formed in a chemical RXN
Free energy
Measure of the capacity of the system to do work (if NEG = spontaneous EXO)
Entropy
The amount of disorder in a system (or environment)
more possible states
Exergonic reaction
Change in Gibbs free E less than zero (Delta G < 0)
spontaneous
Releases heat/Energy
Increasing entropy (High E-> Low E)
Nonpolar -> Polar bonds
Reactants have higher E & Products = Lower E
Still needs trigger to start (activation energy)
Endergonic RXN
Change in Gibbs free E greater than zero (delta G>0) NON spontaneous
Absorbs/requires a input of E to occur
Decreases Entropy
Reactants = Low E & Products = High E
Can be spontaneous if coupled w/ exergonic RXN
Gibbs free-energy change (ΔG)
E of system that can be converted into work
amount of E that is available may be measured only by how it changes in a RXN
First law of thermodynamics:
E is conserved, cannot be destroyed or created only transformed/transferred
Open System
E can enter/exit if it comes from another syst/leaves to another syst
Everything that is alive, earth, E frm sun
Closed System
Nothing gets in/out
-Universe
Second law of thermodynamics:
Spontaneous RXNs, entropy increases when system & environment = considered
state of Entropy(disorder/spontaneous) of the universe/environ will always increase over time
How is Entropy related to PE & bonds?
Low Entropy = High PE (nonpolar bonds)
High Entropy = Low PE (polar bonds)
When you go from Low entropy to High Entropy what is that considered?
Low -> High entropy = Spontaneous (Exergonic)
High -> Low = non spontaneous (Endergonic)
How to calculate change in gibs free E or delta G?
G of products - G of reactants
if pos = endergonic
if neg = exergonic
Catalyze/catalyst
Proteins are specialized to catalyze / speed up chemical RXNs
proteins (catalyst) = enzyme
Enzyme
A protein that functions as a catalyst
Brings substrates together in a precise orientation that makes reactions more likely
Specific for a single RXN – specificity is a product of the geometry & chemical properties of sites where substrate bind
Substrate
A reactant that interacts w/ a catalyst such as an enzyme or ribozyme in a chemical RXN
A surface on which a cell or organism sits